For completeness we also investigated the topological Haldane
model [1]}, [2]}. In this model, in addition to
the on-site potential (which breaks inversion symmetry), a
time-reversal symmetry breaking term is also added, consisting of a
magnetic flux which encircles the center of each hexagon in such a
ways that the Peierls phases (\(\Phi \) ) of the flux only affect the
second nearest neighbor hoppings. The tuning of the on-site potential
and phase on second nearest neighbor hoppings renders possible the
independent control (opening or closing) of each Dirac point
separately. The Hamiltonian now has the form,
\(H = \left[ {\begin{array}{cc}g & f \\f^* & -g \\\end{array} } \right],\) 
